This could be done with just about any bolt action rifle, really. The magazine holds a certain number of rounds, typically five. When you load the rounds into the magazine, the bolt is open. As you close the bolt, it grabs the top round in the magazine and loads it into the chamber. But you can press down on the top round in the magazine so the bolt skips over it and closes without loading it into the chamber. You might want to do this for safety reasons, for example if you wanted the rifle not to have a loaded chamber but yet have quick access to the rounds in the magazine. All you would have to do to make the rifle ready is work the bolt once and you would then have a loaded chamber.
If you wanted a sixth round loaded, you would do as above, but as the bolt began to close over the top round in the magazine you would drop a sixth round in front of the bolt, or directly into the chamber, and close the bolt. The problem is that some actions (military Mausers in particular, excepting some very early models) are designed so that the extractor grabs hold of the cartridge head as it's picked up from the magazine and may not readily snap over the rim of a chambered cartridge, unless you slam the bolt especially hard, which can damage the extractor. So in a straight military Mauser (and probably the Arisaka, which uses a Mauser type extractor) you wouldn't want to make a habit of doing this. Many sporting rifles are designed for the extractor to snap over a cartridge head in the chamber, so it's not an issue with those, but we're not using sporting rifles here.
All in all it would be too fiddly to do in the midst of combat, but one might conceivably load his rifle that way prior to battle, so at least until the first reload he would have six rounds available instead of five. It would be too complicated to implement in game, in my opinion.